Polishing machine and method for polishing optical waveguides

ABSTRACT

The invention relates to a polishing machine ( 10 ) and to a method for polishing optical waveguides, the polishing machine comprising a polishing disk ( 13 ) having a plug socket ( 14 ) for holding a plug with an optical waveguide, a polishing platform ( 15 ) for receiving an abrasive, a positioning device ( 17 ) for relative positioning of the polishing disk and of the polishing platform between a polishing position and a set-up position ( 16 ), and a drive device for executing a relative polishing movement between the polishing platform and the polishing disk in the polishing position, the positioning device having a holder ( 20 ) for detachably holding the polishing disk, wherein the polishing machine has a metering device for applying a rinsing liquid to the polishing platform, a passage opening through which the rinsing liquid is metered onto the polishing platform by means of the metering device being formed in the polishing disk.

The invention relates to a polishing machine and to a method for polishing optical waveguides, the polishing machine comprising a polishing disk having a plug socket for holding a plug with an optical waveguide, a polishing platform for receiving an abrasive, a positioning device for relative positioning of the polishing disk and of the polishing platform between a polishing position and a set-up position, and a drive device for executing a relative polishing movement between the polishing platform and the polishing disk in the polishing position, the positioning device having a holder for detachably holding the polishing disk.

Polishing machines and methods of this kind are sufficiently known and are typically employed to polish optical waveguides or, more precisely, an end of an optical fiber of an optical waveguide. The end of the optical fiber is received in a male connector or plug for the detachable connection of optical waveguides or fiber optic cables. These male connectors serve to establish a plug/plug connection or a plug/socket connection of optical waveguides. The plugs should exhibit as little signal loss as possible and high return loss, which is why the ends of the respective optical fibers are polished together with the respective plug ends, if applicable.

The known polishing machines always have a polishing disk, which forms a polishing attachment and which has fixing devices for the detachable attachment of plugs. A plug attached to an optical waveguide can be detachably attached to the polishing disk in a defined position using the fixing device, the polishing disk being arranged and moved relative to an abrasive layer of the polishing device during polishing. The abrasive layer can be an abrasive that is disposed on a polishing platform of the polishing machine. For example, the abrasive can be a web or sheet of paper or plastic with abrasive particles disposed thereon. The end of the optical fiber in the plug will come into contact with an abrasive layer on the polishing platform and will be polished through the relative movement of the polishing disk, a rinsing liquid typically being added.

Among other purposes, the rinsing liquid serves to cool the optical waveguide or plug and prevents rapid wear of the abrasive or abrasive layer due to wear debris from the plug and the optical waveguide, and it takes away loose abrasive particles from the abrasive layer, thus improving a quality of a polished surface of an optical waveguide.

Depending on its embodiment, the polishing machine can support a plurality of plugs on a polishing disk in order to polish them simultaneously and to thus be able to execute an economically advantageous polishing process. Hence, the polishing disk may also be provided with a plurality of plug sockets having passage openings for receiving an optical fiber or a plug with an optical fiber of an optical waveguide.

In the known polishing methods, a polishing machine is set up by manually attaching a number of plugs each having optical waveguides to a polishing disk, an abrasive or a polishing film or web having abrasive particles being placed on a polishing platform with a polishing pad made of rubber as a support, if needed. A person operating the polishing machine will manually wet the polishing platform or the abrasive located thereon with rinsing liquid. Depending on the type of the polishing machine, the polishing process can be performed by using a positioning device of the polishing machine to transfer the polishing disk from the set-up position into a polishing position, in which the fiber ends and/or the polishing platform are moved relative to the polishing disk by means of a drive device in such a manner that the fiber ends undergo a polishing movement on the polishing platform with the polishing film.

After some time, the polishing platform is returned to the set-up position and the abrasive or the polishing film having abrasive particles on the polishing platform is manually replaced. Since the plugs or the fiber ends and the polishing platform are covered with polishing residue and polluted rinsing liquid, the polishing disk and the polishing platform are typically wiped down with a cloth by the operator in order to ensure, in particular, that no larger abrasive particles remain on the plug ends and that a clean and smooth support surface is available on the polishing platform. Subsequently, a polishing pad with an abrasive having a finer abrasive grit is manually placed on the polishing platform and, after an addition of rinsing liquid, a new polishing process is started. This polishing process is repeated multiple times, each time using an abrasive with a finer abrasive grit than in a previous polishing process. A hardness of the polishing pad can also be varied. This means that the abrasive is changed, the polishing disk and the polishing platform are wiped down and rinsing liquid is added in the set-up position between polishing processes.

Therefore, the object of the present invention is to propose a polishing machine and a method for polishing optical waveguides that allow optical waveguides to be polished at low cost and with high quality.

This object is attained by a polishing machine having the features of claim 1 and a method having the features of claim 13.

The polishing machine according to the invention for polishing optical waveguides comprises a polishing disk having a plug socket for supporting a plug with an optical waveguide, a polishing platform for receiving an abrasive, a positioning device for relative positioning of the polishing disk and of the polishing platform between a polishing position and a set-up position, and a drive device for executing a relative polishing movement between the polishing platform and the polishing disk in the polishing position, the positioning device having a holder for detachably holding the polishing disk, wherein the polishing machine has a metering device for applying a rinsing liquid to the polishing platform, a passage opening through which the rinsing liquid is metered onto the polishing platform by means of the metering device being formed in the polishing disk.

In the polishing machine according to the invention, the polishing platform is configured to receive an abrasive, such as a sheet of paper or a plastic film with abrasive particles adhering thereto. By means of the metering device, the rinsing liquid can now be applied to the polishing platform having the abrasive placed thereon; alternatively, the abrasive can be arranged on the polishing platform together with a polishing pad. In principle, it is also possible for the rinsing liquid to be applied directly to the polishing platform if there is no abrasive disposed on the polishing platform. In particular, a passage opening through which the metering device can meter or apply the rinsing liquid onto the polishing platform is formed in the polishing disk. The passage opening is explicitly not realized as a passage opening for receiving a plug, i.e. as a passage opening of a plug socket, but as a passage opening distinct therefrom.

This allows the rinsing liquid to be applied to the polishing platform and thus also to the abrasive not only in the set-up position but also in the polishing position even if a polishing movement is being executed between the polishing platform and the polishing disk. Thus, the actual polishing process can be used to apply the rinsing liquid by means of the metering device, which means that this process does not have to be performed during set-up of the polishing machine. On the whole, this allows the set-up process between different polishing processes to be shortened, which saves the person operating the polishing machines time and allows the polishing machine to be operated in a more economically advantageous fashion. Since the rinsing liquid can also be applied to the polishing platform or to the abrasive disposed on the polishing platform through the passage opening during a polishing process, an amount of rinsing liquid can also be metered out by the metering device during the entire polishing process. This helps ensure that a sufficient amount of rinsing liquid is present on the abrasive or on the polishing platform at all times during the polishing process. Depending on how the rinsing liquid is metered, particles of the abrasive and material residue or wear debris from the plugs and from the optical waveguides can be prevented from interfering with a polishing effect of the abrasive. A quality of the polished surface can be significantly improved in this way.

The metering device can have a liquid reservoir, a metering pump, a supply line, a metering valve and a controller for a rinsing liquid. The liquid reservoir can be used to store rinsing liquid. The metering pump can be used to pump the rinsing liquid. The supply line can be connected to the metering pump, allowing rinsing liquid to be conducted to the metering valve or directly to the polishing platform via the supply line. The metering valve can be used to control an amount of rinsing liquid discharged. The controller can be used for open-loop and closed-loop control of the modules described. The controller can also be formed by a control device present already for controlling the polishing machine.

The liquid reservoir, the metering pump, the supply line and the metering valve can form a modular metering unit which is removably disposed outside or within a housing of the polishing machine. This allows a conventional polishing machine to be retrofitted with the metering unit or allows a polishing machine to be configured in such a manner from the start that the metering unit can be easily added to it. Furthermore, the metering unit can be easily replaced with a new metering unit in the event of a defect in this case.

The positioning device can have a holder, the holder can have a mount for detachably holding the polishing disk, and the mount can be realized with a magnet for force-fitting support and/or with a coupling for form-fitting support of the polishing disk. The positioning device can have an arm or a boom at whose end the holder is formed. The arm or boom can be of such a design that a contact pressure between the polishing disk and the polishing platform is determined using said arm or boom. This may happen using a bending beam having strain gauges in the boom, allowing a dead weight of the polishing disk to be measured. Moreover, this also allows measuring a force with which the positioning device presses the polishing disk onto the polishing platform to be measured. Based on said force, a polishing force can be calculated and controlled as needed. The mount on the holder also allows the polishing disk to be detached from the positioning device or arm or boom and to be replaced, if required. The mount can be formed by magnets which hold the polishing disk in a force-fitting manner. The magnet can be a permanent magnet or an electromagnet. The polishing disk itself can have a magnet or be made of a ferromagnetic material. Alternatively or additionally, the mount can be a coupling for supporting the polishing disk in a form-fitting manner. For example, an axis disposed on the polishing disk can be plugged into the mount. Said axis can lock with the mount or coupling or, optionally, be wedged or clamped in the mount or coupling, allowing the coupling to hold the axis in a force-fitting manner, as well. If a passage opening is formed in the polishing disk, a supply line can also be routed to the polishing disk on or through the mount.

The mount can permit an inclination of the polishing disk at an angle of up to 2° relative to the polishing platform, the positioning device having a force gauge for determining a contact pressure between the polishing disk and the polishing platform. Accordingly, the polishing disk can swing by said angle when mounted on the mount. This helps ensure that the polishing disk always aligns with the polishing platform and a polishing force is distributed evenly across the polishing disk. The force gauge can be formed within the holder, such as by a bending beam having strain gauges.

The polishing disk can comprise a connecting protrusion to which the mount can be detachably connected. The connecting protrusion can be realized in the manner of an axis that is attached to the polishing disk. In this case, the axis can simply be plugged into the mount.

A channel for conducting a rinsing liquid to the passage opening of the polishing disk can be formed in the mount. If a connecting protrusion is disposed on the polishing disk, the channel can also connect to the connecting protrusion and be routed through it toward the passage opening of the polishing disk. Alternatively, the channel can also end at the mount without being connected to the polishing disk directly. In this case, the polishing disk can be positioned in the mount in such a manner that the channel always ends above the passage opening of the polishing disk, for example.

An atomizer valve of the metering device can be disposed at the passage opening. Using an atomizer valve, rinsing liquid can be sprayed across a large area of the polishing platform. For instance, the entire abrasive can be wetted with the rinsing liquid in this way. Depending on the number of passage openings, more than one atomizer valve may be provided.

A plurality of passage openings through which the metering device can meter the rinsing liquid onto the polishing platform may be formed in the polishing disk. This is particularly advantageous when rinsing liquid is supposed to be metered out in the polishing position since the rinsing liquid can be evenly distributed on the polishing platform or on the abrasive in that case.

The polishing machine may additionally have a cleaning device for applying dry ice to the polishing platform and/or to the polishing disk. The cleaning device can be used to clean the polishing platform and/or the polishing disk substantially without residue. With the dry ice, abrasives and other pollutants on the polishing platform and on the polishing disk, such as loose abrasive particles or material residue and wear debris from the plugs and from the optical waveguides, can be easily removed from the abrasive itself, from the polishing platform and/or from the polishing disk and the respective plugs. The cleaning device applies the dry ice to the respective surface, where the dry ice sublimates because of the significantly higher temperature of the surface, an increase in volume during transition to the gaseous state causing any pollutants to be separated from the surface and eliminated. The transition to the gaseous phase also prevents dry ice residue from remaining on the respective surfaces. Also, any rinsing liquid residue on these surfaces can be easily removed in this way. Compared to manual cleaning, such as using a cloth, a significantly improved cleaning result can be achieved in this way, which, in turn, leads to increased quality of a polishing result. Furthermore, the cleaning device can be used to perform automatic cleaning between polishing processes using different abrasives, which saves a person operating the polishing machine time, thus allowing the polishing machine to be operated in a more economically advantageous fashion.

The dry ice can consist of solid carbon dioxide (CO₂) particles. In particular, the solid particles can be crystals. The dry ice can also be what is known as CO₂ snow. In that case, application of the dry ice to the surfaces to be cleaned can preferably take place by way of a compressed air jet at a temperature of −78.9° C. This will locally undercool and embrittle a layer of pollutants on the respective surface. The solid particles of carbon dioxide penetrate the layer and sublimate, a volume of the carbon dioxide enlarged from the transition to the gaseous phase breaking up the layer and explosively separating it from the respective surface. The carbon dioxide disperses in gaseous form in the ambient air. The surfaces remain undamaged because the dry ice is relatively soft.

The cleaning device can have an application nozzle for dry ice, the application nozzle being usable to form a directed core jet of solid CO₂ particles and a shell jet of compressed air coaxially surrounding the core jet from liquid carbon dioxide and compressed air. The application nozzle can be a nozzle that is centrally supplied with liquid carbon dioxide, which is then discharged to an environment via a central nozzle opening. A ring gap for discharging compressed air can be formed around the nozzle opening, the shell jet thus formed sweeping the liquid carbon dioxide along, which freezes when expanded by the nozzle and turns into CO₂ particles or crystals. The shell jet can focus the core jet onto a surface, i.e. collimate it and direct it at the surface. This significantly improves a cleaning effect of the core jet, i.e. of the dry ice. Also, the compressed air of the shell jet can be used to discharge loosened pollutants to the ambient air. The shell jet can alternatively be formed with nitrogen (N₂).

Another passage opening, through which the dry ice can be metered onto the polishing platform by means of the cleaning device, can be formed in the polishing disk.

At least part of polishing disk and/or of the polishing platform can be coated with an amorphous carbon layer. For example, the amorphous carbon layer can be applied by DLC coating, in which case a surface of the polishing disk and/or of the polishing platform can be fully coated with the amorphous carbon layer. A coating of this kind has a smooth surface with high wear resistance. In particular, a coating of this kind can have a hardness of about 2,500 to 3,000 HV. Moreover, the coating is black in color, making any damage or wear of the coating easy to detect. A service life of the polishing disk and/or of the polishing platform can be significantly prolonged in this way. In particular, the material of the polishing disk and/or of the polishing platform no longer has to be multi-coated in order to achieve a desired hardness of the surface of the polishing disk and/or of the polishing platform. Heat treatment of the polishing disk and/or of the polishing platform can be significantly simplified in this way. On the whole, this eliminates a series of process steps for producing the polishing disk and/or the polishing platform, making production more cost-effective.

Advantageously, the polishing machine can have a changer device, wherein the changer device can comprise a plurality of polishing pads each having an abrasive, wherein the abrasives can be different from each other, wherein the polishing pads with the abrasives can be stored in a magazine of the changer device and can each be arranged on and removed from the polishing platform by means of a handling device of the changer device. For example, the polishing pads can also be different from each other if the polishing pads are made of rubber and have different hardness values. The abrasives can differ in abrasive particle size, i.e. grit, and can be positioned on the polishing pads suitable in each case. The magazine can store a plurality of polishing pads each having abrasives. For example, the magazine can be realized as a circulating belt or a chain in the manner of a paternoster in which the polishing pads with the abrasives are placed or held. The handling device can be a robot arm, a conveyor belt or another suitable device by means of which a polishing pad with an abrasive located on the polishing platform can be exchanged for a polishing pad with an abrasive in the magazine. This also allows polishing pads each having abrasives to be exchanged fully automatically for the execution of a multi-stage polishing process. However, this is not possible unless rinsing liquid can also be automatically applied by means of the metering device.

In the method according to the invention for polishing optical waveguides using a polishing machine, an end of an optical fiber of an optical waveguide is polished, a plug with the optical waveguide being held in a plug socket of a polishing disk, an abrasive being received on a polishing platform, the polishing disk and the polishing platform being moved relative to each other from a set-up position into a polishing position by means of a positioning device, the polishing disk and the polishing platform being moved relative to each other in a polishing movement by a drive device when in the polishing position, the polishing disk being detachably held on a holder of the positioning device, wherein a rinsing liquid is applied to the polishing platform by means of a metering device of the polishing machine, the rinsing liquid being metered onto the polishing platform by means of the metering device through a passage opening formed in the polishing disk. Regarding the advantages of the method according to the invention, reference is made to the description of advantages of the device according to the invention.

Water, preferably distilled water, or a mixture of water and alcohol can be used as a rinsing liquid. The use of distilled or deionized water, in particular, allows avoiding corrosion of the polishing platform and/or of the polishing disk. Should the polishing platform and/or the polishing disk be coated with an amorphous carbon layer, potential corrosion can be precluded, which is why any rinsing liquid suitable in principle can be used in that case.

Rinsing liquid can be metered out before and/or during execution of a polishing movement. This helps ensure that the abrasive is supplied with a sufficient amount of rinsing liquid at all times.

It is particularly advantageous for the rinsing liquid to be metered onto the polishing platform continuously or at intervals during execution of a polishing movement. For instance, rinsing liquid may also be metered onto the polishing platform sequentially. This also ensures that rinsing liquid present on the abrasive is not excessively loaded with pollutants or dirt from the polishing process.

Furthermore, the rinsing liquid may flow from a center toward an edge of the polishing platform. Depending on where the passage opening is disposed or where the rinsing liquid is applied to the polishing platform or to the abrasive, a flow of rinsing liquid from the center to the edge can be established. If the rinsing liquid meets the abrasive in the center of the polishing platform, it will always flow toward the edge as more rinsing liquid is being metered out, where the rinsing liquid, now polluted, can be collected in a circumferential groove and be discharged.

By means of a controlling device of the polishing machine, relative positioning of the polishing disk and of the polishing platform, changing of polishing pads, execution of the polishing movement and/or metering of the rinsing liquid can be controlled. In principle, the controlling device can also be used to control other functions of the polishing machines. By using the controlling device, a polishing process or a sequence of polishing processes can be executed fully automatically. In addition to a metering of rinsing liquid, rinsing liquid may be metered in order to obtain high-quality polished surfaces.

If the polishing machine has a cleaning device, dry ice can be applied before and/or after execution of a polishing movement, preferably in the set-up position. This allows the abrasive or the polishing platform and the polishing disk to be cleaned after a polishing process in order to prepare for a subsequent polishing process, for example. The controlling device can also be used to control a cleaning function of the polishing machines.

Advantageous embodiments of the method are apparent from the description of features of the claims dependent on device claim 1.

Hereinafter, a preferred embodiment of the invention will be explained in more detail with reference to the accompanying drawing.

The FIGURE shows a polishing machine 10 for polishing optical waveguides, polishing machine 10 comprising a housing 11 and a controlling device 12 for controlling a function of polishing machine 10. In particular, polishing machine 10 has a polishing disk 13 comprising a plurality of plug sockets 14. Polishing disk 13 is disposed opposite a polishing platform 15 of polishing machine 10 and is shown positioned in a set-up position 16 relative to polishing platform 15. A drive device (not shown) located in housing 11 can drive polishing platform 10 in a circular movement relative to polishing disk 13. A polishing pad (not shown) with an abrasive can be placed on polishing platform 15.

A positioning device 17 of polishing machine 10 has a linearly displaceable column 18 comprising an arm 19 and a holder 20 for holding polishing disk 13. Holder 20 forms a mount 21 for detachably holding polishing disk 13. An axis 22 that can be plugged into mount 21 is formed on polishing disk 13.

Polishing machine 10 has a metering device (not shown) by means of which rinsing liquid can be metered onto polishing platform 15 having the abrasive placed thereon. Rinsing liquid is supplied through a passage opening (not shown) in polishing platform 15, allowing rinsing liquid to also be applied during a polishing process.

Furthermore, polishing machine 10 can have a cleaning device (not shown) for applying dry ice to polishing platform 15 and/or polishing disk 13. By means of the cleaning device, any pollutants adhering to polishing disk 13 and polishing platform 15 can be eliminated without residue in the set-up position 16 shown. 

1. A polishing machine (10) for polishing optical waveguides, comprising a polishing disk (13) having a plug socket (14) for holding a plug with an optical waveguide, a polishing platform (15) for receiving an abrasive, a positioning device (17) for relative positioning of the polishing disk and of the polishing platform between a polishing position and a set-up position (16), and a drive device for executing a relative polishing movement between the polishing platform and the polishing disk in the polishing position, the positioning device having a holder (20) for detachably holding the polishing disk, characterized in that the polishing machine has a metering device for applying a rinsing liquid to the polishing platform, a passage opening through which the rinsing liquid is metered onto the polishing platform by means of the metering device being formed in the polishing disk.
 2. The polishing machine according to claim 1, characterized in that the metering device has a liquid reservoir, a metering pump, a supply line, a metering valve and a controller for a rinsing liquid.
 3. The polishing machine according to claim 2, characterized in that the liquid reservoir, the metering pump, the supply line and the metering valve form a modular metering unit which is removably disposed outside or within a housing (11) of the polishing machine (10).
 4. The polishing machine according to claim 1, characterized in that the holder (20) has a mount (21) for detachably holding the polishing disk (13), the mount being realized with a magnet for force-fitting holding and/or with a coupling for form-fitting holding of the polishing disk.
 5. The polishing machine according to claim 4, characterized in that the mount (21) permits an inclination of the polishing disk (13) at an angle of up to 2° relative to the polishing platform (15), the positioning device (17) having a force gauge for determining a contact pressure between the polishing disk and the polishing platform.
 6. The polishing machine according to claim 4 or 5, characterized in that the polishing disk (13) comprises a connecting protrusion (22) which is detachably connectable to the mount (21).
 7. The polishing machine according to claim 4, characterized in that a channel for conducting a rinsing liquid to the passage opening of the polishing disk (13) is formed in the mount (21).
 8. The polishing machine according to claim 1, characterized in that an atomizer valve of the metering device is disposed at the passage opening.
 9. The polishing machine according to claim 1, characterized in that a plurality of passage openings through which the rinsing liquid is metered onto the polishing platform (15) by means of the metering device are formed in the polishing disk (13).
 10. The polishing machine according to claim 1, characterized in that the polishing machine (10) has a cleaning device for applying dry ice to the polishing platform (15) and/or to the polishing disk (13).
 11. The polishing machine according to claim 1, characterized in that at least part of the polishing disk (13) and/or of the polishing platform (15) is coated with an amorphous carbon layer.
 12. The polishing machine according to claim 1, characterized in that the polishing machine (10) has a changer device, the changer device comprising a plurality of polishing pads each having an abrasive, the abrasives being different from each other, the polishing pads with the abrasives being stored in a magazine of the changer device and being arranged on and removed from the polishing platform (15) by means of a handling device of the changer device.
 13. A method for polishing optical waveguides using a polishing machine (10), an end of an optical fiber of an optical waveguide being polished, a plug with the optical waveguide being held in a plug socket (14) of a polishing disk (13), an abrasive being received on a polishing platform (15), the polishing disk and the polishing platform being moved relative to each other from a set-up position (16) into a polishing position by means of a positioning device (17), the polishing disk and the polishing platform being moved relative to each other in a polishing movement by a drive device when in the polishing position, the polishing disk being detachably held on a holder (20) of the positioning device, characterized in that a rinsing liquid is applied to the polishing platform by means of a metering device of the polishing machine, the metering device metering the rinsing liquid onto the polishing platform through a passage opening formed in the polishing disk.
 14. The method according to claim 13, characterized in that water, preferably distilled water, or a mixture of water and alcohol is used as a rinsing liquid.
 15. The method according to claim 13, characterized in that rinsing liquid is metered out before and/or during execution of a polishing movement.
 16. The method according to claim 13, characterized in that the rinsing liquid is metered onto the polishing platform (15) continuously or at intervals during execution of a polishing movement.
 17. The method according to according to claim 13, characterized in that the rinsing liquid flows from a center toward an edge of the polishing platform (15).
 18. The method according to according to claim 13, characterized in that dry ice is applied to the polishing platform (15) and/or to the polishing disk (13) by means of a cleaning device of the polishing machine (10).
 19. The method according to according to claim 13, characterized in that relative positioning of the polishing disk (13) and of the polishing platform (15), changing of polishing pads, execution of the polishing movement and/or metering of the rinsing liquid is controlled by means of a control device (12) of the polishing machine (10). 